The present invention relates generally to an apparatus and method for boring screw holes in frame members, and particularly to an apparatus and method for boring screw holes in frame members individually so that the screw holes made in independently bored opposing frame members will align perfectly when the frame members are matingly joined at a miter joint.
The casings of interior windows and doors serve to frame them so as to impart an aesthetically pleasing appearance. When buildings are newly constructed or renovated with new doors and windows, their installation requires that casings be constructed to fit to their particular dimensions. Constructing custom-fit casings with strong and unobtrusive mitered joints requires skilled carpentry and is time-consuming. In today's construction market with an economic imperative to provide quality casings at minimal cost, there is a competitive advantage to reliably making high-quality casings that are pre-drilled for interchangeable assembly on site more quickly and with less skilled labor.
One of the difficulties in achieving this goal, however, is the coincident trend, similarly driven by the need to reduce costs, of making casings out of thinner and thinner pieces of wood. Even with previously used thicker casings, the making of mitered joints at the junction of two or more casing frame members to form the frame around a window or door is a difficult task. Wood is not uniform in quality, and moisture is uneven in cut wood. As a result, the wood of casings is subject to movement caused by changes in its moisture content. Such movement is a critical consideration in joint design. The object of the miter joint is to fix two casing frame members together so that the joint has the greatest possible mechanical strength and is as unobtrusive as possible. Most machine-made joints rely on a combination of mechanical fit and glue for their strength. Screwing two miter-cut casing frame members together to form the joint, greatly strengthens the joint and makes for a casing that will retain its shape for a much longer period of time than one that is simply glued and tacked in place. Miter joints reinforced with screws also enable stronger fittings around doors and windows that are not true.
However, with the thinner casing frames, the making of accurately positioned screw holes is a challenging task. The casing frames used today are generally less than half an inch thick at their thickest and may vary in thickness throughout their width depending on style. For this reason, it is not possible to screw two casing frame members together at a miter joint from the back of one member across the joint and into the other. There is insufficient thickness in the casing frame members to allow for a pilot hole of optimal length for a strong connection without its breaking the surface of the casing if drilled at an angle. Therefore, there is an advantage to placing screws from the edge of one casing frame member through the miter joint to a pilot hole in the mating casing frame member, since longer holes may be drilled lengthwise through a thinner casing than crosswise. To do so, however, requires that the holes be placed precisely so that they remain interior to the casing frame member at all points. This smaller allowable margin of error in situating the holes also requires that the holes be made true and straight, not veering with the grain of the wood, and by a means that prevents splitting of the thinner wood.
Prior attempts to provide a method of making screw holes in frames of other sorts are inadequate to the task and none provide means to quickly and efficiently bore screw holes in frame members independently of one another so that the screw holes will align properly across the miter joint. For example, most machines for drilling screw holes for use at a mitered joint, require that both frame members be positioned in place with the joint formed prior to drilling. This results in perfectly aligned screw holes across only the particular joint formed by those two specific frame members. They are the only ones that will align properly. Requiring that the frame members at each mitered joint be aligned prior to drilling is a time-consuming and labor-intensive task. It also results in individual frame members that are not interchangeable with one another. If damage occurs to one of the opposing frame members, it cannot simply be replaced with another, rather both opposing frame members must be replaced with others drilled in similar fashion.
Another difficulty with this method arises when frame members are lengthy. For example, positioning two casing members to form a miter joint, each of which potentially being 6 to 10 feet in length, is physically impractical.
Still another problem is that these other methods generally screw the hole from the back of the frame. As discussed above, this is not possible with the thinner frame members typically used to form casings. To bore screw holes in casing frame members, boring of the screw hole from the outer edge is required.
Information relevant to attempts to address the problems of drilling screw holes in frame members generally can be found in U.S. Pat. Nos. 5,769,574; 6,142,196; 5,553,645; 4,749,013; 4,603,719; 4,576,213; 3,496,974; 1,956,740 and 1,787,781. However, each one of these references suffers from one or more of the following disadvantages: (a) they situate the screw holes so that screws are placed from the back surface of a frame forward through the miter joint, not from the side of the frame as required with today's thin casing frames; (b) they use drilling devices that rotate at too slow a rate to ensure the making of holes that run true and do not veer with the grain of the wood, a requirement of critical importance with thinner casings; (c) they do not enable the making of holes rapidly and reliably enough to ensure cost-efficiency; (d) they require that both mating members of a frame be clamped in place prior to drilling in order to make mating holes perfectly aligned in each member (though the holes are only aligned for the two particular frame members), an inefficient method and a practical impossibility when working with casing frame members of long lengths in the range of 6 to 10 feet; and, (e) they do not enable the making of pocket- and pilot-holes separately in individual casing frame members such that the holes are precisely placed and aligned to enable a perfect mating at the miter joint and the interchangeability of casing frame members. None provide a means for producing framing members that may be used interchangeably to form miter joints at which their respective screw holes align perfectly.
For the foregoing reasons, there is a need for an apparatus and method for efficiently and cost-effectively making precisely positioned and aligned mating first and pilot screw holes in separate frame members so as to enable their interchangeability. There is still further a need for an apparatus and method to make the screw holes from the sides of narrow frame members with precision and speed in order to ensure a true trajectory through only the interior of the frame and to avoid splitting in frames made of wood.